<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="./vue.js"></script>
  <style>
    .box {
      width: 100px;
      height: 100px;
    }
  </style>
</head>
<body>
  <div id="app">
    <span>R</span>
    <input type="text" v-model="r"><br>
    <span>G</span>
    <input type="text" v-model="g"><br>
    <span>B</span>
    <input type="text" v-model="b">
    <hr>
    <div :style="{background:`rgb(${r},${g},${b})`}" class="box"></div>
  </div>
  <script>
    const vm = new Vue({
      el:'#app',
      data:{
        r: 254,
        g:90,
        b:0
      },
      methods:{
         
      }
    })
  </script>
</body>
</html>